The present invention relates to a washing machine, and more particularly, to a washing machine having a damper which can attenuate vibration and noise induced during an initial operation of a washing cycle or a dehydrating cycle due to unbalanced laundry contained in a spin basket.
A washing machine 1 includes an external casing 2 for constituting an external appearance, as shown in FIG. 24. A tub 3 containing water for washing and a spin basket 4 which is rotatably installed in the tub are provided in the external casing. The tub 3 is supported by suspended strings 6 movably in the external casing. A pulsator 5 for forming a rotating water current flow for washing, is provided at the bottom of the spin basket 4. A driving motor 7 and a shaft assembly 8 are installed at the lower end of the tub 3, and selectively rotate the spin basket 4 or the pulsator 5 in a predetermined direction according to a program of a controller (not shown) to perform washing and dehydrating cycles.
Meanwhile, during the washing cycles, vibration of the tub 3 occurs due to the rotation of the spin basket 4. The vibration of the tub 3 severely occurs during the dehydrating cycle in which the rotational speed of the spin basket 4 increases. In this case, the size of the vibration is determined according to weight of the laundry and the degree of the unbalance thereof contained in the spin basket. That is, if the weight of the laundry contained in the spin basket lays disproportionate to one side, the spin basket 4 inclines at a corresponding side. As a result, the spin basket 4 collides with the tub 3 during rotation to induce vibration due to mutual contact. Thus, an efficient washing operation of the laundry is prevented by the inclined rotation of the spin basket 4, and generates noise due to excessive vibration.
Thus, to solve such a vibration problem, a conventional washing machine 1 includes the suspension support 6 as shown in FIG. 24. The suspension support 6 includes a suspension bar and a friction buffer 6' which is provided at an end of the suspension bar and fixed to the tub 3. The friction buffer 6' includes a friction cover shaped in the form of a bell, and a friction member and a resilient spring which are provided in the friction cover, to thereby attenuate constantvibration transferred to the tub 3, that is, up-and-down linear vibration.
However, when laundry of more than a prescribed capacity is contained in the tub, the suspension support 6 cannot properly perform vibration attenuation, since the suspension support 6 is mounted initially according to the location of the center of weight in a no-load state of the tub. The suspension support 6 attenuates only up-and-down vibration. Thus, if the spin basket 4 rotates in a disproportionate way in a left-and-right direction due to the disproportionate laundry, such left-and-right vibration is transferred to the tub 3. Accordingly, the left-and-right vibration transferred to the tub 3 induces a wobble of the tub 3 which is suspension-supported in the external casing to thereby prevent a washing machine from operating smoothly. When the wobble thereof is severe, excessive noise is generated due to frictional contact with the external casing 2.
Thus, a washing machine having a system for attenuating the irregular and nonlinear vibration of the spin basket 4 has been recently proposed. U.S. Pat. No. 5,269,159 discloses an example of a washing machine having such a system. In such a washing machine, a sensor is provided for detecting a distance between the tub 3 and the external casing 2, and electromagnets are mounted on mutually opposing outer surfaces. Thus, if the distance between the tub 3 and the external casing 2 which is detected via the sensor is closer than a reference distance, a mutual repelling force is induced between the opposing electromagnets while a mutual attraction force is induced therebetween in a contrary situation, to accordingly maintain a constant distance between the tub 3 and the external casing 2.
However, the above-described conventional washing machine includes a complicated circuit structure to cause cost to be high. Also, it may not be very efficient to attenuate the vibration of the spin basket 4 via the circuit structure. Also, even in the washing machine having a damper which has been proposed in a different form, the structure is complicated and the left-and-right vibration of the tub 3 generated according to the rotational movement of the spin basket 4 cannot be efficiently attenuated.